Control system



Dec. 5, 1939.

B. CHANCE CONTROL sYs'EM 2 Sheets-Sheet 1 CLM? -2 Sheets-Sheet 2 5, 1939- B. CHANCE CONTROL SYSTEM Filed neo. 21, 1957 Patented Dec. 5, 1939 PATENT OFFICE amor:

connor. mm

man came. mm. N. s. massa@ member zi. 1m, sam n. 181.048

nomma. icl. 11szw 'rms invenusneistes au. novel motor control system which is capable of general use in any system wherein it is desired to control some condition. 'I'hls system is particularly adapted for use in automatic steering systems for dirigible craft, such as ships, to maintain the craft on its course.

More particularly, the invention relates to control systems of the type employing light-sensitive devices for controlling the operation of la motor;

for example in the case of an automatic steering system, such devices control actuation of the steering element, such as a ship's rudder, in response to deviation of the craft from its course.

The invention has for its principal object the provision of an improved motor control system embodying the features set forth hereinafter.

. A more specific object of the invention is to provide a light3control1ed system wherein the effectiveness of the light-sensitive devices is controlled in a' novel manner to obtain certain results, among which is the compensation for time delay or lag which is inherent in any telemotor system. In the case of an automatic steering system, the action of the rudder motor is varied wheneverthe craft changes its direction of yaw or deviation from its course t'o thus compensate for the lag in the telemotor system and, if desired, to give the rudder a relativeLv great throw. By this action, the rudder motor is caused to operate for a relatively great period whenever the .craft changes its direction of yaw, the throw of the rudder being in a direction to tend to overcome the yaw or deviation and bring the craft back on its course. If the craft yaws successively in the same direction, the subsequent successive rudder throws are in proportion to the magnitude of the successive yaws or deviations. When the craft again reverses its direction of yaw. the rudder motor is caused to operate for a relatively great period in the opposite direction, thus compensati'ng for the time delay or lag in the telemotor system and, in some instances, giving the rudder a relatively great throw.

Another object of the invention is to provide a system of this character wherein the effectiveness of the light-sensitive devices is controlled automatically to prevent response to transient deviations of the conditions being controlled. In an automatic steering system, this feature of the invention provides automatic weather contro The term weather contro as applied to systems of this character, refers to the control which prevents the system from functioning in response to transient yaws or deviations of the craft as distinguished from yaws of the craft atlts natural period. The automatic weather control of the present invention serves two important functions: iir'st, it renders the system insensitive to transient deviations, and second, it renders the system insensitive to repeated operations of the rudder. especially in opposite directions, thereby preventing "hunting".

. Still another object of the invention isto provide a system of this character employing an auxiliary light-sensitive cell which controls an alarm indicator causing itto give an indication whenever a yaw or deviation is greater in amplitude and/or duration than that normally encountered, and which auxiliary cell also controls novel latching means for control tubes associated with the other cells. The alarm indicator also warns of any unnatural electrical or mechanical condition in the entire system.

Other objects and features of the invention will appear hereinafter.

In the accompanying drawings:

Fig. 1 is a diagrammatic illustration oi' a simple steering system in which the present invention may be employed:

Fig. 2 is a plan view of the optical portion of the system of Fig. i:

Pig. 3 is a diagrammatic illustration of the electrical circuits of the system; and

Figs. 4 to 8 are explanatory illustrations of the light beam and principal control cells.

Since the invention is particularly adapted for use in an automatic steering system, it will be described in its application to such a system,

-although it is to be understood that the invention isnot limitedtosuchasystem. y

For the purpose of the present description, the diagram of Fig. .1 will suiiice to illustrate the general arrangement of a light-controlled steering system in which the present invention may be employed. As shown in Fig. l, a reiiector is mounted at the axis of a compass card and receives light from a light source above' the compass card and axially aligned therewith. The

reflector projects a light beam onto a lightsensitive control unit carried by a support which pivots about the axis of the compass card and is mounted on the craft so as to be movable relative to the stationary light beam in accordance with deviations of the craft from its course in one direction or. the other. The light-sensitive control unit functions to control the apparatus described hereinafter, which apparatus, in turn,

.controls the motor lmit'which operates the rudder.

granted December 14, 1937. to which reference maybehadfordetailswhichperseformno part of the present invention. As shown in l'ig. 2, the system may comprise two outer light-sensitive cells L and R which control the steering motor, and a center light-sensitive cell C whose purpose in the present instance will be described later.

In Pig. 8. there is shown a circuit diagram of an illustrative form of the invention. 'I'he lightsensitive cells L and R are arranged to control the multi-grid vacuum tubes V1 and V1, respectively, each of the grids of which is capable of cutting of! the plate current of the tube. 'nie tubes V1 and V1- control the grid-controlled rectiiier tubes R1 and R1, respectively. 'Ihe latter tubes serve to rectify the electrical energy from the supply transformer T, and also serve to control the application of unidirectional current to the reversible D. C. motor M. 'I'his motor, of course, corresponds to the motor of Fig. 1. The motor drive and the follow-up are indicated by the broken-line representations which are intended to represent any conventional drive and follow-up. It is unnecessary to illustrate these in detail, since they may take any suitable form; for example, they may take the form illustrated in my above-mentioned patent. It will be understood that the follow-up drive will operate in any instance to elect follow-up movement of the light-sensitive cell devices in a direction opposite to the control movement of the cell devices which caused operation of the motor.

The rectifier tubes R1 and R1 also control the energization of a relay Il, the purpose of which will be described later. In the specinc illustration. the relay Il comprises a pivoted arm Ia carrying contacts at its upper and lower ends which are adapted to engage stationary contacts. A spring lib urges the arm counterclockwise. 'I'he winding 2l acts against the action of this spring. 'Ihe other winding 2i operates a springbiased latch llc.

'I'he tubes R1 and R1 also control a double-diode tube R4 to effect certain functions, as described hereinafter. At present, it suiiices to state that the relay Il and the tube Rs control the operation of tubes V1 and R1 and thus control the relative eectiveness or sensitivity of the cells L and R.

The center cell C operates through a control tube V. to control a second tube Vs which controls a relay Il, which in turn controls the energization of an alarm indicator Il, as described hereinafter. 'I'he indicator may be an audible indicator, such as a bell, or it may take any other suitable form 'Ihe cell C also serves to latch the tubes V1 and Vr through the medium of tube V. and relay Il, as described hereinafter.

A source of electrical energy, which may comprise a transformer T1 and a full-wave rectifier R1 supplies the necessary unidirectional voltages for the tubes V1, Vx. V., and V. It will be noted that resistors I8, I4, II, il and I1 are connected between the positive supply conductor il and the negative supply conductor l. 'I'he direct current flowing through these resistors sets up voltages across them having the polarities indicated. and these voltages serve to bias the tubes, as will be apparent. It will be noted that the voltages across resistors Il and i1 apply a fixed negative bias to the grids gs of tubes V1 and Vf, respectively, through the cells L and R; the voltage across resistor I1 also applies a negative bias to the gridoftubeVathroughcellCinoppositionto the voltage across the lower portion of resistor il; and tbe voltage across resistor -ii applies a positive bias to the grid of tube V. It will be apparent also that a voltage is established across potentiometer Il, the lower portion of which is included in circuits which include the resistors Il and 4i, resistors 2l and Il, resistors I1 and Il. and cells L and R, respectively. The cells L and R vary the negative potential applied to the grids moftubesv1andvrbyvaryingthecurrent flow in these circuits, thus varying the voltage drops across resistors I1 and 4l.

'I'he system of Fig. 8 may be clearly understood by considering the operation of the system with reference to the illustrations of Figs. 4 to 8 showing various relative positions of the light beam and the two outer cells L and R. l'ior the sake of simplicity, the center cell C has been omitted from these figures since the center cell may be disregarded in the explanation with reference totheseilgures. IneachoftheFlgures4to8. the light beam is illustrated by a broken-line representation. As illustrated. the light beam may be assumed to be of substantial width in order that it may function in the manner described hereinafter in conjunction with the cells L and R. Although in the device of Fig. l. the cells move and the beam remains stationary, and it is convenient to have the apparatus thus arranged in the case of an automatic steering system, to facilitate the explanation, we may consider that the beam moves relative to the light cells and we may speak in terms of movement of the beam. Obviously, the result is the same whether the beam is moved and the cells remain stationary, or vice versa.

Before considering the specinc operation of the system of Fig. 3, it is necessary to bear in mind certain features of the system. It should be noted nrst that the relay Il is always in one or the other of its operative positions and is held in such positions by the spring and latching arrangement illustrated. Moreover, the tubes V1 and Vrare each of such character that the grid o: of each tube is capable of biasing the tube to plate current cut-off regardless of the potential on the grid an. In the operation of these tubes. the plate current is controlled by the grids but each tube is always operated over the portion of its characteristic curve below the point at which the grids would draw current. 'Ihe characteristics of these tubes is such that an increase in positive potential on their grids q1, that is making the grids less negative, decreases the sensitivityof the tubes. The positive potentials which are applied to the grids, as described hereinafter, do not cause the grids to draw current but decrease the potential of the grids. When ever plate current flows in .the tubes V1 and V1, the voltages established across the resistors I0 and 21 are effective to bias the grids of rectiners R1 and R1- sufilciently negative to reduce the current supplied to the motor ,M below the value of current necessary to operate the motor.

In normal operation of the system, the beam will have two principal positions which are shown' in Figs. 4 and 5. respectively. When the beam is in the position of Fig. 4, the relay contacts 22 and 22a will be closed, while the relay contacts liandawillbeop'cned. Whenthebeamisin the position of Fig. 5. the reverse will be true, that is, the contacts 2l and 22a will be opened, while thecontactsandawillbeclosed.

Letitbeassumedflrstthatthebeamisinthe position of Fig. 4, the closed contacts 22 will then apply a positive potential to the grid or of tube V1, which potential is derived from the voltage gisant' l '3 -drop resistors I3. Il and il and is applied to thm over conductors 32 and 2l, resistor 2l. and conductor I4. This positive potential decreases the sensitivity o! the tube Vr and maintains the decreased sensitivity ot that tube as longasthebeamisinthepositionofllig. 4. It will be seen, therefore, that when the beam is in the position oi Fig. 4, the eilectivens oi cell R is low. On the other hand, the eiiectiveness oicellLishighbecausetheopenrelaycontacts 2l remove the positive potential from the grid ga of tube Vx which would be applied trom the resistors i3, i4 and Il over the conductor II. resistor Il and conductor 2i ii the contacts 23 were closed.

. Suppose now that the control movement causes the beamto moveiromtheposition ofllg.4to the position ot Pig. 8. In the esse oi' an automatic steering system, such control movement would, of course, be caused by the deviation of the craft from its course. Bearing in mind that the cell L is effective, it will be seen i'rom Fig. 8 that the increased light on this cell will cause an increase in the voltage drop across resistor 41 which will increase the negative bias on the grid as of tube Vi, and this increase in negative bias is sumcient to reduce the plate current of the tube to ,cut-oil. The diminishing current ilow through resistor 20 reduces the negative bias on the grid of the rectifier Ri, causing the rectifier tube to supply increasing unidirectional current to the motor M to start the motor. It may be noted here that the condenser 2O is simply a by-pass condenser for A. C. components. I'he unidirectional current nowing through the left hand field coil of motor M causes the motor to operate in a direction to correct the condition which started the operation of the system. In the case oi an automatic steering system, the motor throws the rudderin a direction to bring. the craft back on its course. At the same time, the follow-up mechanisms eilect relative movement between the beam and the cells in a direction opposite that of the control movement, so as to deenergize the motor after a time interval. In other words, in etlect, the follow-up action will cause thebeam to move from the position oi' Fig. 6 back to the position of Fig. 4, at which time the motor will be deenergized, aswill be explained further presently.

In the meantime, theienergization of the left I hand motor circuit energizes the coil 2i of relay i0 but, since the relay contacts 22 and 22a are already closed, the energization of coil 2i has no enect. At the same time, however, the increas-l ing current flowing through the primary of transformer T.- induces current in the secondary and sets up a voltage across the potentiometer Ps, and a portion of this, voltage is applied to. the right hand diode oi tube Re. rendering the diode conductive and causing a voltage to build up acros's the condenser 2l. This voltage is applied over conductor 2l to the grid a: of tube Vr to decrease further the sensitivity oi tube Vr which, in turn, reduces further the eil'ectiveness of cell R. The condenser 24 and its shunt resistor 25 comprise a time-delay circuit having a predetermined time constant, -so that it requires a predetermined short time interval for the condenser to discharge through the resistance. Thus, the further reduction in the edectiveness or cell R is maintained for a predetermined time interval during which any transient movement oi' the beam over cell R will have no effect. Buch transient movement 0i the beam might be caused byawaveinthecaseoi'ashlporbyaometranaientconditlonorerrorofacontrolmechanism.

As the beamis returned by the follow-up action toward the position oi Fig. 4, the negative biason thegridgsoi'tubeviis decreased and. when the beam reaches the position o! lig. 4, the bias is decreased suillciently to permit the plate current oi' the tube to increase, thus increasing the voltage across resistor 2l which restores the negative bias to the grid of rectiner Ri and eilects gradual deenergisation of the motor M.

It the beam moves repeatedly from the position of Fig. 4 toward the left to some position such as that of Pig. 6, the above-described operation will be repeated and, in the case of an automatic steering system, the rudder will be given suillcient successive throws during the successive intervals required i'or the follow-upto bring the beam back to the position of Fig. 4, or the steering motor speed will tend to match the speed of yaw of the vessel.'

Suppose now that the beam reverses its direction of control movement and moves from the position o! Fig. 4 to the pomtion of Fig. '1. In this instance. the beam will traverse the cell R but it will be remembered that the effectiveness of cell R is low by virtue of the positive bias on the grid a: of tube Vr. However, substantial movement oi' the beam over cell R is not required to make the cell respond, asthe light is already predominantly on cell R. 'The increasing light on cell R increases the negative bias on the grid a: of the tube Vl suiliclently to cause cut-oil' oi' the plate current of the tube. 'Ihe diminishing current ilow through the resistor 21 reduces the negative bias on the grid of rectifier Rr and eii'ects energization ot the right hand circuit oi the motor M, as will be apparent from the above description. 'I'he motor, therefore, operates in a direction opposite that of the operation considered above, and the follow-up is operated accordingly to eiect follow-up relative movement between the beam and the cells.

In the mean time, the winding 28 of relay l0 is energized, opening the..contacts 22 and 22a and closing the contacts 2l and 23a. The latch mechanism of the relay holds it in this position as illustrated. The opening of contacts 22 removes the positive potential from grid a: oi' tube Vl, thus increasing the negative potential on the grid and increasing the enectiveness of cell R. Due tothe increased effectiveness oi cell R, the grid gz of tube Vl is maintained sumciently negative to maintain plate current cut-ot! of the tube until the beam is moved to the position of Fig. 5 by the follow-up action. Hence, the motor M conv tinues to run until the beam reaches that position. The running of the motor for a relatively long period compensates for the time lag in the telemotor system and in some instances. may give the rudder a relatively great throw which is commonly referred to as initial rudder" action in automatic steering systems.

The closing of contacts 23 applies a positive potential to the grid a: oi tube Vi over the conductors 32 and It, resistor 30, and conductor 36. This decreases the sensitivity of tube Vi, permitting the movement of the beam to the position of Fig. 5 without any eilect from cell L attempting to cause motor operation in the reverse direction. f f

In the meantime, current ilowing in the righthand motor circuit induces current in the secondary of transiormer Tt. The induced current flowing through potentiometer P1 establishes a voltage thereacross, and a portion of this voltage is applied to the left hand diode of tube Rs. rendering the diode conductive. Consequently, a voltage is built up across the condenser 2t, which voltage is applied over conductor ll to the grid Us of tube Vx. This further reduces the sensitivity of tube V1, which, in turn, further reduces theeectivmeaaoiceiln Duetothetimeconstant of the time-delay circuit 1l, Il, the voltage thereacross is maintained for a predetermined ahort. interval during which the condenser 2l discharges through the resistance 3l.. During this interval, the extremely low effectiveness oi cell L prevents this cell from responding eilectively to any transient deviation of the beam toward the left even though such transient deviation might carry the beam over a substantial portion ot the cell L. In other words. even ii the beam were to be deflected toward the left beyond the position oi' Fig. 5, the cell L would not respond ei'lectiveiy. Thus, in the case of automatic steering, the system is rendered non-responsive to any transient 'yaw during the time interval established by the time constant of circuit 2l. Il. 'Ihe effectiveness of cell L is not ao low, however, that full light on it would cause no operation.

As long as the beam remains in the position oi Fig. 5 as distinguished from the position of l'lg. 4. the relay ill is maintained in the position shown with the contacts -closed and the positive bias applied to the grid a: of tube Vx so that the sensitivity o! the tube V1 is maintained at a low value. During this time. the sensitivity of the tube Vr is high. owing to the continued removal of the positive bias from the grid ya of that tube by virtue oi' the open contacts 22.

Suppose now that the beam moves from the position of Fig. 5 toward the right. The increasing light lon the highly etl'ective cell R causes increase in the negative bias on the grid o: oi' tube Vx. causing plate current cut-oi! oi' the tube V as will be clear from the above description. Consequently, the rectifier Rr is rendered elective to energize the right hand circuit oi the motor M, causing operation of the motor which, in turn, eilects follow-up action to bring the beam hack to the position of Fig. 5. At the same time, the winding 2l is energized but the relay is already in the position shown. At the same time, however, current is induced in the secondary oi transformer T: and a voltage is established across potentiometer P1. rendering the lett-hand diode of tube Rs conductive and building up a voltage across condenser 2l, which is applied for a predetermined short interval to the grid o: of tube Vi, further decreasing the sensitivity of that tube, as above described, and preventing elective response oi cell L to any transient deviation oi the beam to the lett. When the followup action has returned the beam to the position oi Pig. 5. the negative bias on the grid a: oi tube Vf is reduced suinciently to cause ilow of plate current through resistor 2l, thus restoring the bias on the grid of rectiiier Rr and causing deenergixation oi motor M. In other words, the operation in response to movement oi the beam from position of Fig. 5 toward the right is similar to the above-described operation which takes place when the beam moves from the position of Fig. 4 toward the left, except that in one case, the R controls the` operation by virtue of its being highly ei'iective compared to the low eilec- ,isavrv tivenessofthecellhwhileintheothercasathe cell L is eilective whilethe cell R is ineiiective.

It is important to note that the movement oi thebeamfromthepositionotl'lg.5toward the right causes relatively short operation of the motor M due to the high eilectiveness o! the cell R. The period during which the motor is operated is dependent upon the amplitude of movementoithebeamacrossthecelllinresponse to the deviation which causes such movement. Ii' the beam moves repeatedly from the position of Fig. 5 toward the right, the motorM will be operated repeatedly and each operation oi the motor will be determined by theamplitude of the particular beam movement causing the operation.

When the beam moves from the position of Fig. 5 toward the left, the cell L increases the negative bias on the grid o: of tube Vi suiiiciently to cause .plate current cut-oil. thereby rendering the rectiiier R1 eil'ective to energize the lefthand circuit of motor M. As a result, the relay i0 is operated, as will be understood from the above description. opening contacts Il and 23a and closing contacts 22 and 22a. This removes the positive bias from the grid n: of tube V1 and applies a positive potential to the grid o: oi tube Vr. as will be clear from the above description. Consequently, the tube Vr is rendered eiiective or sensitive, while the sensitivity of tube Vr is decreased, causing decrease in the eiiectiveness of cell R. The sensitivity of tube Vf will be further decreased ior a short interval by the application to the grid an thereof of the voltage which builds up across condenser 2l, as will be understood from the above description. Due to the high eectiveness of the cell L, the motor Il willbeoperateduntilthebeamismovedbythe follow-up action to the position of Fig. 4. I'hus the motor will be operated for a relatively long period, as above described.

It will be seen from the above description that each time the beam reverses its direction of movement, the motor Mis operated for a relatively long period, thus compensating for the time lag in the telemotor system, while successive movements ot the beam in the same direction cause operation oi the motor for successive relatively 'short periods which are determined solely by the amplitude oi such movements.

Itwillbeseeniurtherthatwhenoneoithe cellsLandRiscontrollingthe systeminresponse to deviations in one direction, the eii'ectiveness of that cell to threshold light is high while the effectiveness o! the other cell to thrhold light is low. At all times, each cell causes motor operation in response to substantially the same percentage change o! light irrespective of the amount of light on the cell. Each time a deviation takes place in the direction of the prevailing yaw, the eilectiveness or sensitivity oi thecellwhoseeiiectivenesshasalreadybeenreduced. is further reduced ior a predetermined short interval to prevent that cell i'rom respor ing eii'ectively to any transient yaw in the oppusite direction. In the case ot automatic steering, this is termed "automatic weather control", theetlectoiwhichistopreventthesystemi'rom responding to transient yaws such as niight be causedbyawavestrikingthecraitorbyerror inaomepartoitheapparatussuchasthecompass. By adjustment oi P1. Pa and M, both the magnitude and the time constant ot the automatic weather control may be adjusted. It will beapparentalsothattheamountbywhichthe sensitivity of the tubes V1 and vg may be reduced is adjustable by means of the potentiometer M. By proper design and adjustment. the system as applied to automatic steering may be made to( respond only to yaws of the craft at its natural period and may be made non-rcsponsive to transient yaws such as above mentioned. In other words, any sizeable ship will have a natural period of yaw and such yaws 10 will be longer in duration than any' transient yaws. Advantage is taken of this diil'erence in duration of the two types oi yaws and the system is designed to discriminate between them as above described. v

Thus iar in the consideration of the operation oithesystemthe centerceliChasbeendisregarded. AswlllbeobviousiromFigs.4to'iand from the above discussion, during normal operationoithesystem, the beamwillmoveov'era rangewhichwillnotbemu'chgreaterthanthe range denned by the beam positions ci' Figs. 4 and 5, and the beam will impinge constantly 90u the center cell C. This cell serves to control the alarm indicator u tn roush the medium or tubes Vs and Vs, and it 'also serves to latch the tubes V1 and Vr as will be described presently. Aslongasasmallpartoithebeamimpingesupon the center cell C, a suiilcient negative bias is applied to the grid ci tube Va from the resistor I1 to prevent ilow ot plate current in that tube. Under such conditions, the plate current ilow oi tube Vs builds up a voltage across the condenser Il which is applied to the winding oi relay I i and holds the relay open. thus maintaining the alarm indicator l2 inoperative. Suppose, however, that the beam moves on oi the center cell, for example Suppose that the beam moves to the extreme lett hand position shown in Fig. 8. The rponse oi the cell L tothe passing of the beam ther causes energization of the winding 2| ci relay il, as above described, which actuates the relay to close contacts 22 and 22a, it they are not already closed. In the meantime, the beam leaving the center cell C will decrease the negative bias on the grid of tube Vasufllciently to permit plate current ilow through the resistor Il, and the voltage across that resistor will apply a suilicient negative bias to the grid oi tube Vs to cut o3 the plate current of that tube, causing the condenser 3l to discharge through the winding oi relay H. The condenser and winding constitute a time-delay circuit whose time constant is such that if the large deviation of the beam persists for a predetermined period, the relay winding is deenergized due to the dissipation oi the voltage across condenser 3|, thus closing the energizing circuit oi the alarm indicator l2. The effectiveness oi the center cell C to eiect the operations Just described may be controlled by varying the position oi the tap on resistor I 6. In other words, the effectiveness oi the center cell C to control the potential on the grid of tube Vs may be varied by varying the portionroi resistor it below the movable tap thereof.

In the meantime, the closing of relay contacts 22a. applies a negative potential from the 'resistor il to the grid a: of tube Vi over the conductors 3! and 4l. This negative potential is suiilcient to maintain plate current cut-oft of the tube V1, it being remembered that the grid Us is capable of cutting oi! the plate current regardless of the potential of grid ya. Thus, the closed relay contacts 22a latch the tube V1 in plate current cut-ofi condition which, in turn, maintains the rectifier Ri n operative, causing the motor M to operate con- .tinuously until the follow-up action restores the normal relative positions oi the beam and cells. When the beam again impinges upon the center cell C, the cell increases the negative bias on the grid oi tube V., cutting oi! the plate current oi that tube and removing the bias voltage from across resistor ll. 'I'his removes the bias from the grid oi tube Vs causing plate current ilow in that tube and consequent energization oi relay Il to interrupt the circuit oi the alarm indicator I2, and it also removes the negative bias from the grid a: of tube V1, unlatching the latter tube. Thus, the system is restored to normal operation.

I! the beam should move ci! the cells in the opposite direction leaving the center cell. the alarm indicator l2 will be rendered operative as before but, in this instance. the response oi.' the cell R will energize the winding 2| oirelay i0, closing contacts 23 and 22a and opening contacts 22 and 22a. 'I'he clodng oi contacts 23a will then apply `a negative bias from resistor 3l to grid as 0i tube Vlover the conductors ll and 4I. This latches the tube vr in plate current cut-oil.' condition, causing -the motor M to run continuously until the follow-up action restores the normalv relation between the beam and cells.

In connection with the above-described operation, it should be noted here that the resistances l2 and Il are very high compared to the resistance 28 so that they do not ailect the voltage across the resistor Il. The sole purpose oi the resistances 42 and is to prevent the grids a: of the tubes Vx and Vli'rom floating,

It may now be noted that, although the relay contacts 22a and 23a are alternately closed during the normal operation of the system as first described above, the closing oi' these contacts has no eect upon the tubes V1 and Vr, since .there is no voltage across the resistor Il. Therefore, during normal operation, the relay Il may operate without having any latching eect upon the tubes Vi and Vr. In other words, the center cell C controls the latching oi' the tubes V1 and Vr and, as long as the light beam impinges on the cell, there can be no latching of these tubes.

From the above description. it will be apparent that the system provided by the invention functions to control the sensitivity oi' tubes V1 and Vr thus controlling the effectiveness of the cells L and R in response to control movements between the beam and the cells, the sensitivity control effecting relatively great operation of the motor M whenever the direction of control movement changes. Moreover, the sensitivity of tubes V1 and Vr is varied to eiect automatic weather control. This so-called automatic weather control, which is obtained by the functioning of either the time-delay circuit 24, 25 or the similar circuit 29, 30, also serves to prevent hunting.

Sincethe time-delay circuits are slow acting in restoring the sensitivity of the tubes V1 and Vr, vthey tend to prevent any hunting action. For example, when the cell L is controlling the system. the time-delay circuit 24, 25 operates to reduce vthe sensitivity of the tube Vr, and the discharge 0f the time-delay circuit is gradual so that the sensitivity level of the tube Vr is raised very slowly. In like manner, when the cell R is controlling the system, the time-delay circuit 29, 30 functions to raise the sensitivity level of the tube V1 very slowly following the reduction in the sensitivity oi the tube by the said circuit. As a result, if the light is on a cell whose effectiveness is gradually increasing, the motor will run at a'speed determined not only by the amount of light on 6 aisafnv thecell but also by the rate at which the ei'lectiveness of the cell increases. and the motor will move the cells slowly toward a neutral position. IftbeeifectivenessofthecellsLandRissogreat s that no neutral position exists, the time-delay circuits will prevent oscillatory action or in other words, will serve to damp the system, greatly increasing the period of any "hunting" action and thus eliminating wear on the motor. The

1o automatic weather control enables the use of extremely high sensistivity without continual "hunting". While in the system illustrated, the automatic weather control is applied only to the nonoperative cell, it is apparent that the control may 1s be readily applied to the operating cell as well to thus further damp the system.

It will also be apparent from the above description that the invention provides a novel latching arrangement by means of which the tubes Vi and Vr are latched under control of the center cell C and this cell also functions in a novel manner to control an alarm indicator. By means of these features, the motor is maintained in operation whenever the beam leaves the center cell until the follow-up action restores the normal condition and at the same time an alarm is given if the beam remains off the center for any appreciable period of time.

While the rectiiiers R1 and R are employed 80 herein to control the motor circuits, the invention is not limited to such devices, since any suitable circuit closing device may be employed.

The condensers II, I0, Il. Il, 5I and I4 are by-pass condensers.

In a specific example, a system constructed as illustrated employed the following devices and values:

Tubes Vi and V were type 6L? tubes. TubesRi andRrweretype CGAtubes. o IubeRawasatypeHtube Tube V. and Vs were type 6C5 tuba. TubeRiwasatypeXtube. The cells L, C and R were conventional phototubes. 5 Resistors u, ls and n were iooo ohms mn.

Resistor It had a value of 250 ohms. Resistor Il had a value of 500 ohms. Resistors 2l and 11 were 20,000 ohms each. Resistors 25, 3l and $1 each had a value of 1 50 megohm.

Resistor Il had a value of 0.5 megohm. Resistors l2 and 43 were 8 megohms each. Resistor 44 had a value of 3000 ohms. Potentiometers Pi and Pa each had a value of 1000 u ohms.

Resistors 41 and 48 were 5 megohms each. Resistors "and l5 each had a value of 0.1 megohm. m Resistor 5l had a value of 5 megohms.

Resistor 58 had a value of 5000 ohms. Condensers 24 and 29 were each 4 microi'arads. Condensers 28 and 5I were each 0.5 micrcfarads. Condenser 3| had a value of 500 microfarads. Condensers Il, l2 and 5I were each 0.002 microu farads.

Condenser 50 had a value of 0.02 microfarad Condenser l1 had a value of 1 roicrofarad. Condenser 54 had a value of 20 microfarads. The motor M was a 1A H. P. split series D. C.

motor. Y The transformers T: and T: each had a step-up turn ratio of 1 to 50.

As previously stated, the invention is applica- 1g ble for uses other than automatic steering. For

example, the control system provided by the mvention may be used in a furnace temperature control system to control a motor adapted to operate a fuel valve. In such case, the control movement of the light beam over the cells may be 5 obtained by means of a galvanometer which may be deflected in accordance with temperature variations of the furnace, as is well understood in the furnace temperature control art. When applied to such use, the system of this invention will l0 control the fuel valve in a manner to keep predetermined constant temperature within the furnace in the same manner that the system serves to maintain a craft on its course in the case of automatic steering. The control actions 1s described above will serve the same general functions in the application of the system to furnace temperature control. The alarm feature and the latching feature will likewise function whenever the furnace temperature deviates widely I0 from the desired temperature and will serve a useful purpose in such systems.

It will be apparent. therefore, that the invention is applicable to `various uses and furthermore it is capable of various embodiments other M than the specific form illustrated and described herein for the purpose of disclosure.

I claim:

1. In a motor control system, a pair of lightsensitive devices, a source of a light beam for 80 varying the electrical characteristics of said devices, said devices and said source being constructed and arranged to provide for relative movement between the devices and the beam, whereby the beam traverses said devices in one 85 direction or the other, an electric motor, means controlled by said devices in response to said relative movement for energizing said motor, follow-up means operably by said motor to eiIect relative movement between said devices and said beam. to thus eifect deenergization of said motor, and means responsive to activation of one device by the beam for decreasing the effectiveness of the other device for a predetermined time interval, to thus prevent response of said other device to transient relative movement between the beam and the devices.

2. In a motor control system, a pair of lightsensitive devices, a source of a light beam for varying the electrical characteristics of said devices, said devices and said source being constructed and arranged to provide for relative movement between the devices and the beam, whereby the beam traverses said devices in one direction or the other, an electric motor, means controlled by said devices in response to said relative movement for energizing said motor, follow-up means operably by said motor to effect relative movement between said devices and said beam, to thus effect deenergization oi' said motor, 50 means responsive to activation of one device by the beam for increasing the eifectiveness of said one device and for decreasing the eectiveness of the other device, and additional means for further decreasing the eifectiveness of said other ss device for a predetermined time interval during each activation of said one device. to thus prevent response of said other device to transient relative movement between the. beam and the devices. 7o

3. In a rn'otor control system, a plurality of light-sensitive devices. a source of a light beam for varying the electrical characteristics of said devices, said devices beng constructed and arranged for control movement relative to the beam 1g "snaar-1? A 'tnebeamtosgamimpimemsaidaumia'ryoeto vary the incidence o! the beam on said devices, an electric motor. means responsive to control movement oi said devices i'or energizing said motor, follow-up means operable by said motor 5 to eil'ect follow-up movement of said devices, to

thus effect deenergization oi the motor, an auxiliary light-sensitive device constructed and arranged to receive said beam during normal operation, and means responsive to substantial and "1'0 prolonged non-incidence of the beam on said auxiliary device i'or indicating abnormal control movement of said devices.

4. In a motor control system, a pair of lightsensitive devices, a source of a light beam for varying the electrical characteristics of said devices, said devices and said source being constructed and arranged to provide for relative movement between the devices and the beam, whereby the beam traverses said devices in one 'gq direction or the other, an electric motor, means including a bias-controlled vacuum tube connected to each of said devices for controlling the energization of said motor, follow-up means op- A v erable by said motor to eiiect relative movement as between said devices and said beam, to thus enect deenergization oi said motor, an auxiliary lightsensitive device, and means continued by said auxiliary device for latching at least one of the y bias-controlled tubes in motor energizing con '30 dition whenever the beam leaves said auxiliary device, to thus maintain energization of the motor until-the follow-up means causes the beam to again impinge on said auxiliary device. Y Y

`5. In'a motor' control system, a pair of lightsensitive devices, a source of a light beam for varying the electrical characteristics of said devices, said devices and said source being constructed and arranged to provide for relative movement between the devices and the beam, 40 whereby the beam traverses said devices in one direction or the other, an electric motor, means including a bias-controlled vacuum tube connected to each o f said devices for controlling the l, energlzation of said motor, follow-up means operable by said motor to eiect relative movement between said devices and said beam, to thus effect deenergization of said motor, and means responsive to abnormally great or prolonged control movement of said devices for latching at least '50 one of the bias-controlled tubes in motor energizlng condition.

6. In a motor control system, a pair oi' lightsensitive devices, a source of a light beam for varying the electrical characteristics of said devices, said devices and said source being constructed and arranged to provide i'or relative movement between the devices and the beam,

whereby the beam traverses said devices in one' direction or the other, an electric motor, means responsive to said devices for controlling the enegization of said motor, follow-up means operable by said motor to eiiect relative movement between said devices and said beam, to thus eiiect deenerf gization of said motor, an auxiliary light-sensitive device constructed and arranged to receive said beam during normal operation, means responsive to substantial and prolonged non-incidence oi.' the beam on said auxiliary device for 7o indicating abnormal control movement, and means controlled by -said auxiliary device for latching said first-mentioned means in motor energizing condition whenever the beam leaves said auxiliary device, to thus maintain energization oi' the motor until the follow-up means causes vice.

'1. In a motor control system. a pair of lightsensitive devices, a source ci a light beam for varying the electrical characteristics oi' said de- '5 vices, said devices and said source being constructed and arranged to provide for relative movement between the devices and the beam, whereby the beam traverses s aid devices in one direction or the other, an electric motor controlled l0 by said devices, follow-up means for effecting follow-up relative movement between said devices and said beam in response to energization oi' said motor. means for rendering one o! said devices effective and the other oi said devices l5 relatively ineii'ective, whereby the quiescent state oi said system obtains when said beam impinges predominantly upon the relatively inen'ective de-- vice. and means responsive to beam traversal of the relatively ineffective device for rendering such device effective and for rendering the eiiective device relatively ineffective, whereby the quiescent state of said system obtains when said beam impinges predominantly on the device last rendered ineiiectlve.- 26

8. In a motor control system, a pair of lightsensitive devices, a source oi' a light beam for varying the electrical characteristics oi' said devices, said devices and said source being constructed and arranged to provide for relatlveao movement between the devices and the beam, whereby the beam traverses said devices in one direction or the other, an electric motor controlled by said devices, follow-up means for eiiecti.; ing follow-up relative movement between said 'Il devices and said beam in response to energizetion of said motor, means for rendering one oi said devices effective and the other ol.' said devices relatively ineiective, whereby the quiescent state oi.' said system obtains when said beam impinges predominantly upon the relatively inedective device, means responsive to each beam traversal oi' the effective device for rendering the other device further ineii'ective, means responsive to beam traversal of the relatively ineiective device for :a rendering such device effective and for rendering the effective device relatively ineiieetive, whereby the quiescent state of said system obtains when said beam impinges predominantly on the device last rendered ineiective, and means responsive rg0 to each beam traversal oi' the device last rendered eiiective for rendering further ineffective the device last rendered ineffective.

9. In a motor control system, a pair of lightsensitive devices, a source of a light beam for "s varying the electrical characteristics of said devices, said devices and said source being constructed and arranged to provide for relative movement between the devices and the beam,

whereby the beam traverses said devices in oneo'o direction or the other, an electric motor oontrolled by said devices, follow-up means for ei.'- fecting follow-up relative movement between said devices and said beam in response to energizetion of said motor, means for rendering one of f 8 aisaviv the eiiective device relatively ineiiective. wherebythequiescentstateoisaldsystemobtainswhen said beam impinges predominantly on the device last rendered ineiiective, and means responsive to l each beam traversal ci the device last rendered edective for rendering further ineiiective ior a predetermined time interval the device last rendered ineii'ective.

l0. ln an automatic steering system for dirigil ble craft. electro-optical means constructed and amngedsoastoberesponsivetodeviationsoi the craft from a predetermined course, a steering motor operable by said electro-optical means to bring the crait back on its course. follow-up l. means for restoring the normal condition oi said electro-optical means in response to energimtion otsaidmotor,andmeansresponsivetoopera tions oi the system in one direction for preventing operation o! the system in the opposite direction steering motor operable by said electro-optical meanstobringthecraitbackonitscoursaiollow-up means ior restoring the normal condition u otsaidelectm-optical meansinresponsetoenergiaation ci' said motor, and means including a timecircuitoperablebyeachoperationoithe systeninonedirectiontorendersaidelectmoptical means temporarily insensitive to yaw oi the crait in the opposite direction, thus preventing operation of the system in the opposite directioninresponsetoyawingoithecraitatarate Q l2. In an automatic steering apparatus for dircrai't, an electro-optical system constructed andarrangedtoproduceelectrical eiiectsinresponsetodeviationsoithecraitiromapredetermined course, a steering motor operable by u saidelectrical eiiectstobringthecraitbackon its course, follow-up means for restoring the normal condition oi said electro-optical system in response to energimtion oi' said motor, means responsive to change in direction of the crai'ts .o yawing motion i'or adjusting said electro-optical system to vary the eiiects produced thereby, and means responsive to successive yawing movements of the craft in the same direction ior iurther adjusting said electro-optical system so as gs to prevent response to transient yaws oi the crait in the opposite direction.

13. In a motor control system, a pair oi' lightsensitive devices. a source oi a light beam for varying the electrical characteristics o! said de- U vices, said devices and said source being constructed and arranged to provide for relative movement between the devices and the beam to vary the incidence oi the beam on said devices. a pair oi control tubes connected respectively to I said devices. an electric motor controlled by said control tubes. means ior relatively biasing said control tubes so that one is rendered sensitive while tbe other is rendered relatively insensitive, thus rendering one of said devices eii'ective and Il the other device relatively ineiiective. whereby the quiescent state of said system obtains when said beam impinges predominantly upon the relatively ineiiective device, means responsive to beam traversal oi' the relatively ineiiective device .iosreversingtherelativebiasesoisaidcontrol' tubes, and means for eiiecting follow-up relative movement between said beam and said devices.

14. In a motor control system, a pair oi lightsensitive devices. a source oi a light beam ior varying the electrical characteristics o! said del vices,saiddevicesandsailsourcebeingconstructed and arranged to provide ior relative movement between the devices and the beam to vary the incidence oi the beam on said devices. a pairoicontroltubesconnectedrespectivelytolo said devices. an electric motor controlled by said .controltubes,meansiorrelativelybissingsaid control tubes so that one is rendered sensitive while the other is rendered relatively insensitive. thus rendering one oisaid devices eiiective and u the other device relatively ineiiective, whereby the quiescent state oi said system obtains when said beam impinges predominantly upon the relatively ineiiective device. means responsive to eachbeamtravessaloitheenectivedevice for increasing the relative biases of said control tubeameansresponsivetobmtraversaloithe relatively ineiiective device ion reversing the relativebiasesoisaidcontroltubandmeans for eiiecting follow-up relative movement between said beam and said devices.

l5. Inamotorcontrolsystemapairoilightsensitive device, a source ot a light beamior "UIN the electricalcharacteristics oi said deviceasaiddevicesandsaidsourcebeingcon-p structed and arranged to provide for relative movement between the devices and the beam to varytheincidenceoi thebeamonsaiddevices.a pair oi control tubes connected respectively to said devices. an electric motor controlled by said l control tubes. meam i'or relatively biasing said control tubes so that one is rendered sensitive while the other is rendered relatively insensitive. thus rendering one'oi said devices eective and the other device relatively ineiiective. whereby o the quiescent state of said system obtains when said beam impinges predominantly upon the relatively ineiiective device. means responsive to each beam traversal oi the eiiective device i'or increasing the relative biases of said control tubes u ior a predetermined time interval, means responsive to beam traversal of the relatively ineiiective device for reversing the relative biases of said control tubes. and means for eecting follow-up relative movement between said beam 5o and said devices.

16. In a motor control system, a pair of lightsensitive devices, a source oi a light beam for varying the electrical characteristics of said devices, said devices and said source being consg structed and arranged to provide for relative movement between the devices and the beam to vary the incidence oi the beam on said devices,

a pair oi control tubes connected respectively to said devices, a pair of grid-controlled rectieo ners connected respectively to said control tubes. an electric motor controlled by said rectiiiers. means for relatively biasing said control tubes so that one is rendered sensitive while the other is rendered relatively insensitive. thus renderes lng one oi said devices eii'ective and the other device relatively ineiiective, whereby the quiescent state of said system obtains when said beam impinges predominantly upon the relatively ineffective device. means responsive to beam trav- 'lo ersal of the relatively ineiiective device for reversing the relative biases of said control tubes, and means ior eii'ecting follow-up relative movement between said beam and said devices.

17.Inamotorcontrolsystem.apairoilight yg sensitive devices, a source or a light beam for varying the electrical characteristics of said devices, said devices and said source being constructed and arranged to provide for relative movement between the devices and the beam to vary the incidence of the beam on said devices, a pair of control tubes connected respectively to said devices, a pair of grid-controlled rectiilers connected respectively to said control tubes, an electric motor controlled by said rectiers, means for relatively biasing said control tubes so that one is rendered sensitive while the other is rendered relatively insensitive, thus rendering one of said devices effective and the otherdevice relatively inefiective, whereby the quiescent state oi said system obtains when said beam impinges predominantly upon the relatively ineliective device, means responsive to each beam traversal of the eiiective device for increasing the relan tive biases of said control tubes for a predetermined time interval, means responsive to beam traversal of the relatively inenective device for reversing the relative biases of said control tubes, and means for eiecting follow-up relative movement between said beam and said devices.

18. In a motor control system, a pair of lightsensitive devices, a source of a light beam for varying the electrical characteristics of said devices, said devices and said source being constricted and arranged to provide for relative movement between the devices and the beam, whereby the beam traverses said devices in one direction or the other, an electric motor. means responsive to said devices for controlling the energization of said motor, means for normally rendering one o! said devices effective and the other device relatively ineiiective, whereby the system responds to beam traversals of the eiiective device, means responsive to beam traversal in the other direction for rendering said other device eiiective and said one device relatively ineiective, whereby the system responds to beam traversals of said other device, and follow-up means for eilectlng follow-up relative movement between 45 said devices and said beam in response to energization oi said motor.

19. In-a motor control system, a pair o! lightsensitive d I a source of a light beam for varying the el al characteristics of said devices, said devices and said source beingconstructed and arranged to provide for relative movement between the devices and the beam, whereby the beam traverses said devices in one direction or the other, an electric motor, means including a control tube connected to each of said devices for controlling the energization oi said motor, means for normally sensitizing one tube and desensitizing the othentube, whereby the system responds to beam traversals of one of said devices, means responsive to beam traversal in the other direction for desensitizing said one tube and sensitizing said other tube, whereby the system responds to beam traversals of the other oi said devicesand fllow-up means for effecting follow-up relative movement between said devices and said b'eam in response to energization of said motor.

20. In a motor control system, a pair of lightsensitive devices, a source of a light beam for varying the electrical characteristics of said devices, saldvdevices and said source being constructed and arranged to provide for relative movement between the devices and the beam, whereby the beam traverses said devices in one direction or the other, an electric motor, a pair of multi-grid control tubes for controlling the energization of said motor, means connecting each of said devices to a grid of the associated control tube, follow-up means operable by said motor to eilect relative movement between said devices and said beam, to thus effect deenergization of said motor, an auxiliary light-sensitive device, and means controlled by said auxiliary device for biasing an auxiliary grid oi the effective control tube to latch the tube in motor energizing condition whenever the beam leaves said auxiliary device, to thus maintain energization of the motor until the follow-up means causes the beam to again impinge on said auxmary device.

BRITION CHANCE. 

